Ignition devices for gas burners



Jan. 9, 1968 cs. w. ROBEIIRTSHAW 3,362

7 IGNITION DEVICES FOR GAS BURNERS Filed Aug. 5, 1965 2 Sheets-Sheet 2 GRAHAM WILLIAM Raaekrsmw INVENTOR':

United States Patent .0

3,362,455 IGNITION DEVICES FOR GAS BURNERS Graham W. Robertshaw, Timperley, England, assignor to North Western Gas Board, a corporation of Great Britain, Northern Ireland and the Isle of Man Filed Aug. 3, 1965, Ser. No. 476,869 6 Claims. (Cl. 158-123) This invention relates to ignition devices for gas burners, which consume either town gas or any other fuel gas, either alone or as a mixture with air.

It may be a safety requirement with any burner installation or combustion system that a flame-detection device is provided so that, through suitable means, the gas supply shall be automatically turned off in the event of extinction of the flame, for any reason whatsoever.

In one quite common arrangement, ignition and reignition of the main burners is provided by pilot jets while the flame-sensing device is of the thermocouple type with its own activative pilot flame; but in such an arrangement initial ignition of the pilot burners has to be provided by a lighted taper, or other external means.

Electric spark-ignition burners are known having an insulated electrode projecting through the end of the burner and flame sensing means are known which employ the electrical conductivity of the ionised gas as the sensing factor.

The object of the present invention is to combine such known art.

According to the invention, a combined spark ignition and flame-sensing system for a burner for combustible gases comprises a spark ignition electrode constituting one side of a spark gap efl'ectively located in the flame ionisation zone of said burner, electric means for energising the spark ignition electrode, a flame-detection device responsive to electrical conductivity eifect of a flame in a circuit therewith, and switch means for bringing said spark gap into circuit with said flame-detection device or alternatively with said electric means for energising said igition electrode.

The spark gap may be energized with a high voltage for ignition or may be connected in series with a flamedetector of known kind. The present invention is concerned with the arrangement provided for achieving the above alternatives. Thus, the ring of the burner, which constitutes one side of the spark gap is grounded and the probe which constitutes the other side of the spar-k gap is connected to one side of the secondary winding of a transformer. The other side of the secondary winding of the transformer is connected with switch means 21 which may be actuated to connect the other side of the secondary winding of the transformer either directly to ground or to ground through the flame-detector device of known kind.

When the switch 21 connects the secondary winding directly to ground, the primary windings of the transformer may be energized by means of the switch 26 with either alternating current or interrupted direct current to cause a spark in the gap for ignition purposes. After ignition the switch means 21 will be moved to the alternate position to connect the spark gap in series with the flame-detector and during this time the primary winding of the transformer will, of course, not be energized. Thus, when the flame-detector is operative, the secondary winding of the transformer merely constitutes a connecting lead without any voltages being induced thereacross from the primary windings.

The combined spark ignition and flame-sensing system aforesaid may be characterised in that the said electrode is housed within the burner.

3,362,455 Patented Jan. 9, 1968 The invention will be further apparent from the following description, with reference to the several figures of the accompanying drawings, which show, by way of example only, a number of embodiments thereof.

Of the drawings:

FIG. 1 shows a longitudinal section of a first example of a spark ignition burner with which the invention may be practised;

FIG. 2 shows a longitudinal section of a second examv ple of a spark ignition burner with which the invention may be practised;

FIG. 3 shows a circuit diagram of one example of a combined spark ignition and flame sensing system in accordance with the present invention; and

FIGS. 4 and 5 show fragmentary diagrams of further spark ignition burners for use with the system according to the present invention.

As shown in FIG. 1, the burner comprises a metal body 10 with a burner plate 11 having a central aperture against which the end of the insulator 12 of a spark electrode 13 is sealed in such a manner as to prevent light-back. The electrode may be enclosed in an insulating conduit or sleeve 14 with spacing members 15. The electrode projects through an elbow body 16 and ends in a connection terminal 17 similar to that of an engine sparking plug.

As shown in FIG. 2 the body 10 and burner plate 11 are of the same construction and electrical connection to the electrode 13 may be provided either at 17 (as in FIG. 1) or in the side of the body as shown at 18. The electrode is spring loaded at 19 to ensure that the insulated end 12 is held into the burner plate in efiective seal therewith irrespective of diiferential expansion effects caused by heating of the body 10 from the flame while the electrode remains relatively cool by reason of the flow of gas within the burner and the small area of exposure to the flame at the combustion end.

As shown in FIG. 3 the ignition system includes a transformer with the secondary coil 20 in circuit with the electrode and an electric switch 21 providing alternative circuit through earth at 22 or at 23 through a flame detection device 24, also earthed at 25. A 2-pole switch 26 enables current such as AC. or interrupted DC. to be supplied to the primary coil 27 of the transformer.

As shown in FIG. 4 the transformer may be in the form of a unit 28 located within the body 10 of the burner or as shown in FIG. 5 in a housing 29 attached to the side of the burner body.

The switch 21 is shown located at the relatively earthed end of the secondary coil.

In use, the switching means 21 may enable the transformer to provide an electric spark across the gap between the electrode and burner plate for ignition purposes or may normally hold the flame detection device 24 in circuit with the gap between the electrode and burner plate that is in circuit with the ionised gas at the burner plate so that conductivity of the ionised gases at the burner may be used to maintain the supply of gas thereto, or the absence of such conductivity may be used in known manner to activate a shut-oif valve mechanism for the gas supply.

It will be appreciated that it is not intended to limit the invention to the above examples only, many variations, such as might readily occur to one skilled in the art, being possible, without departing from the scope thereof, as set forth in the appendent claims.

What I claim is:

1. A combined spark ignition and flame sensing system for a burner for combustible gases comprising a spark ignition electrode constituting one side of a spark gap eflectively located in the flame ionization zone of said burner, electric means for energizing the spark igition electrode comprising a transformer having primary and secondary windings, said secondary winding having a hot side and a grounded side, said electrode being connected to said hot side, a flame detection device for sensing the electrical conductivity effect of a flame in circuit with said secondary winding and switch means having two positions in said grounded side which, when in one position, connects said grounded side with the other side of said spark gap directly, and, alternatively, when in another position connects said grounded side with said other side through said flame detection device, and further switch means for energizing said transformer.

2. A system according to claim 1, wherein a housing is provided around said burner, said transformer in sealed relationship with said housing.

3. A system according to claim 2 wherein said primary winding is energized by alternating current.

4. A system according to claim 2 wherein said primary winding is energized by interrupted direct current.

5. A system according to claim 2 wherein said burner comprises a tubular body plate having apertures therein and closing one end of said body, and an insulating sleeve located in a bore in said plate through which sleeve said electrode protrudes.

6. A system according to claim 5 wherein said sleeve and said bore are of complementary conical shape, and including resilient spring means urging said sleeve into pressurized engagement with said bore from the rear of said burner plate.

References Cited UNITED STATES PATENTS 2,241,295 5/1941 Clark 158-115 2,996,113 8/1961 Williams 158-115 3,002,550 10/1961 Schreter 158-28 3,265,114 8/1966 Childree 158-123 FREDERICK KETTERER, Primary Examiner. 

1. A COMBINED SPARK IGNITION AND FLAME SENSING SYSTEM FOR A BURNER FOR COMBUSTIBLE GAS COMPRISING A SPARK IGNITION ELECTRODE CONSTITUTING ONE SIDE OF A SPARK GAP EFFECTIVELY LOCATED IN THE FLAME IONIZATION ZONE OF SAID BURNER, ELECTRIC MEANS FOR ENERGIZING THE SPARK IGNITION ELECTRODE COMPRISING A TRANSFORMER HAVING PRIMARY AND SECONDARY WINDINGS, SAID SECONDARY WINDING HAVING A HOT SIDE AND A GROUNDED SIDE, SAID ELECTRODE BEING CONNECTED TO SAID HOT SIDE, A FLAME DETECTION DEVICE FOR SENSING THE ELECTRICAL CONDUCTIVELY EFFECT OF A FLAME IN CIRCUIT WITH SAID SECONDARY WINDING AND SWITCH MEANS HAVING TWO POSITIONS IN SAID GROUNDED SIDE WHICH, WHEN IN ONE POSITION, CONNECTS SAID GROUNDED SIDE WITH THE OTHER SIDE OF SAID SPARK GAP DIRECTLY, AND, ALTERNATIVELY, WHEN IN ANOTHER POSITION CONNECTS SAID GROUNDED SIDE WITH SAID OTHER SIDE THROUGH SAID FLAME DETECTION DEVICE, AND FURTHER SWITCH MEANS FOR ENERGIZING SAID TRANSFORMER. 